updated TurbSim.docx with discussion on how periodic files can be created by entering UsableTime as "ALL"
updated TurbSim.docx with discussion on how periodic files can be created by entering UsableTime as "ALL"

git-svn-id: 0cc9220f43ab8845d531ce07eb12ab2ea9270d70@55 c49df35f-aca6-4ea5-bb27-7fcdbeda79b9

OpenFAST/OpenFAST,OpenFAST/OpenFAST,OpenFAST/OpenFAST